Typically, a header for a harvesting machine includes a cutterbar which is operable to cut standing crop as the machine moves forward and a rotatable reel which carries tines to engage the standing crop and sweep it towards the cutterbar for cutting and then carry the cut material towards an auger before releasing it. The auger usually consolidates the cut crop material centrally of the header before it is passed on to an elevator and therefrom into the body of the machine for processing. The position of the cutterbar in relation to the auger is critical and in general depends on the type and condition of the crop to be harvested. Small grain crops usually allow a relative small distance between the cutterbar and the auger, while crops such as long-stemmed grains and canola are harvested better with the cutterbar set at a larger distance from the auger. For these reasons the cutterbar and the associated table section may be made adjustable in a generally fore-and-aft direction of the header.
Known systems, as described in EP-A-0 250 649, provide a series of outer guides with associated inner sliding guides for moving the table forward or backwards in relation to the header frame. A problem associated with these is the metal-on-metal contact limiting the lifetime of the guides. Using replaceable metal wear blocks in the front of the header is known, but a problem with these is that dirt is scooped in front of the header due to the location of the wear blocks. Furthermore, the vertical range of the movable header is limited by the extra space taken by the wear blocks. The minimum stubble height is hereby limited.
Another problem with current U-shaped or rectangular guides is the lateral movement that is caused by the side movement of the knives. The guides have some lateral clearance and the forces generated by the knife movement on the frame are significant, in such a way that the movable table continuously shifts sideways during cutterbar operation. This limits the lifetime of the header considerably.
It is therefore an object of the present invention to limit the lateral movement of the movable header table and to increase its lifetime.